Fabrication of carbon bodies



March 2, 1965 Filed Nov. 29. 1960 O. PETER ETAL FABRICATION OF' CARBON BODIES musi@ 2 Sheets-Sheet l Pif/02465772505 l l l INVENTORS.

March 2, 1965 Filed Nov. 29. 1960 O. PETER ETAL FABRICATION OF' CARBON BODIES 2 Sheets-Sheet 2 ffl-WKK .74@ .0/.4

United States Patent Gti 3,171,816 Patented Mar. 2, 1965 of Germany Filed Nov. 29, 1960, Ser. No. '72,492 Claims priority, application Germany, Dec. 3, 1959,

s claims. (ci. 252-510) The present invention relates to agents for reducing the softening point of binding pitch, as used in the fabrication of carbon bodies.

For the fabrication of carbon bodies the petroland/ or coal tar pitch coke having a certain gradation of grain sizes and being used 'as dry material, is mixed with a binding agent, preferably coal tar pitch, and formed in the usual manner. Then the carbon body is baked in a furnace at about 1000 C. and, if necessary, subjected to a graphitization process at temperatures above 2000 C. When baked in the furnace, the binding pitch carbonizes to form a coke skeleton that cements the individual grains of coke and imparts a corresponding strength to the carbon body. Since the strength depends, in general, on the yield of coke of the binding agent, the artificial carbon industries prefer as binding agents pitches having a softening point that is as high as possible. However, there are technological limits with respect to the utilization of pitch since a pitch that has a high softening point requires a higher processing temperature when being mixed and pressed. ln order to overcome these ditliculties, the softening point of pitches that have a high softening point is reduced to a lower softening point. As agents reducing the softening points of binding pitches there were used hitherto coal tar or higher fractions of coal tar having an oily consistency. However, these known agents have the drawback that the yield of coke of the binding agent, calculated on the binding pitch, remains practically unchanged since the agents themselves do not furnish any coke or only a small portion of coke, i.e. the binding agent, is, so to speak, only fluxed by the substances used for reducing the softening point. This, however, results in a deterioration of the quality of the carbon bodies obtained with respect to their specic weight, strength and volume of voids since, when baking the carbon bodies, a greater quantity of gas escapes than in the case of baking the carbon bodies that do not contain agents for reducing the softening points of the binding pitches. Moreover, it was found that the agents used hitherto only bring about a slight reduction of the softening point due to the partly high viscosity of said agents.

Now we have found that the drawbacks of the known agents reducing the softening points of the binding pitches can be avoided when using for the fabrication of carbon bodies according to the invention organic compounds that are soluble in the binding pitch and contain one or more active double or triple bonds, singly or in admixture with one another, as agents reducing the softening points ofthe binding pitches.

According to the invention, those organic compounds have proved to be especially advantageous that contain one or several C=C-, CEC (for example, unsaturated hydrocarbons, vinyl or acetylene derivatives), C=O (for example, ketones, aldehydes, quinones, C=NH (for example imines), CEN (for example nitriles), C=S (thio compounds, for example xanthates), or N=N compounds (azo compounds).

When using the proposed compounds as agents that reduce the softening points of the binding pitches, there are obtained, while adding the same amount of agent, not only a greater reduction of the softening point of the binding pitch but lsimultaneously also a partly considerable increase in the yield of coke of the binding pitch as compared with the use of the formerly applied agents.

FIGS. l and 2 of the accompanying drawings represent diagrams illustrating the dependence of the softening point and the yield of coke of a binding pitch on the quantity added of the agents reducing the softening points of the binding pitches as used hitherto and as used according to the invention.

In FIG. 1, there are indicated in the ordinate, in C., the softening points, determined according to Krmer- Sarnow, of a pitch used as a binding agent, and in FIG. 2 the yields of coke of said pitch determined according to Elektrokemisk, calculated on the pitch used, and in the abscissa there is indicated, in percent by weight, the respective addition of the agents reducing the softening points of the binding pitches.

PEG. 1 shows that when using, according to the invention, phthalodinitrile, azobenzene, styrene or phenylacetylene as agents reducing the softening points of the binding pitches, the softening points of the binding pitches are reduced in a higher degree than in the case of the tar oils used hitherto, while FIG. 2 distinctly shows that by using the roposed agents the yieid of coke of the binding pitch is simultaneously increased appreciably.

In Table l, there are listed a number of organic cornpounds that may be used as agents reducing the softening points of the binding pitches according to the invention, said compounds containing one or several active carboncarbon bonds; in rTable 2 there are listed compounds containing one or several active carbon-oxygen bonds, and in Table 3 those compounds containing one or several active carbon-nitrogen bonds. In the second column there is listed the respective addition of the agent reducing the softening points of the binding pitches (in percent by Weight), in the third column the softening point determined according to Krmer-Sarnow, and in the fourth column the yield of coke of the binding pitch determined according to Elektrokemisk` The figures given in brackets in the third and fourth columns refer, respectively, to the values of the pure binding pitch without the addition of an agent reducing the softening point of said pitch.

The selectively dehydrogenating effect of the proposed agents reducing the softening points of the binding pitches must especially be stressed, which effect is due to the fact that said agents condense by oxidation only part of the compounds present in the coal tar pitch, for example fluorene, acenaphthene, carbazole derivatives and other compounds with relatively easily mobile hydrogen atoms, while another part, for example chrysene, pyrene, etc., is not dehydrogenated. lt is, therefore, decisive for the action of the additives according to the invention that, in addition to their solubility in the binding pitch which brings about a reduction of the softening point', their dehydrogenating action, on the one hand, is strong enough to dehydrogenate compounds of coal tar pitch with mobile hydrogen but that, on the other hand, the action is not strong enough to bring about a dehydrogenation at the aromatic nucleus itself. Thanks to this selective dehydrogenation, no change can be ascertained in practice in the properties of the binding coke obtained from the pitch after baking, properties such, for example, as the thermal ratio of expansion, the capability for being graphitized and the hardness, in spite of an increase in the yield of coke of the binding agent. This is of great importance especially for carbon bodies that are to be subjected to a subsequent graphitization process since all condensing agents for increasing the yields of coke proposed hitherto such, for example, as sulfur, metal oxides and metal chlorides, organic nitroand chlorine compounds, -oxygen compounds and compounds that yield oxygen, due to their strong oxidizing action, dehydrogenate the compounds present in the binding pitch to such a degree that the binding coke obtained therefrom has a high coeicient of expansion and a reduced capability for being graph- 816 4 however, are not intended to limit the invention thereto, the parts being by weight:

Example 1 Twenty kilos of coal` tar pitch coke which has, in all itized. Moreover, when4 using, Yfor example, nitrocom- 5 poundsA and oxygenfyielding substances such, for example, examples, the Same' gladllcn 0f gf 3111 S1265, 1-eas peroxides, there are formed large amounts of water in the course of the dehydrogenation which, especially in parts 075 12 mm' the fabrication of carbon, impairs the structure and, 40 Vparts-().O6-0.75 mm. thereby, also the strength of the carbon body. 10 50 arts O 06 mm As compared with. theV known agents for reducing the p softening points. of the binding pitches, the compounds are mixed.' Wlll 5 t0 5-5 kllOS 0f flfy Plcll Scflenlng according to the present invention possess many advan P01nt7`8`- C en dthe agents Tedllclng the softening Polnls tages, for example, when using the proposed compounds, of the binding pitches enumerated in the following table the softening pointsof. the binding pitches are much more (Percent by Welgll'fo calculated en llle Welgllt 0f 'Elle dry reduced although adding, in eachV case, the same amount Pitch Used) al 120* C- tC l60- C nclrfolfnedY 1n the of the agent which amounts to a decrease of the dynamic usual manner 011 a hydrauh QXtruder Into round elecviscosity since the softening points determined according tl'cfles hel/lng a d lnnlelef 0f' 70 mln-i baked 1n the flng toV Krmer-Sarnow must be regarded as the equiviscosity furnace nl 1.000" C' `f01` 3 Weeks and Subsequently temperature for the viscosity of about 10'I cp. By re 20 glapnl'nZed 1n he uSUalnanne1 ducing the viscosity of the binding pitch, therefore, either The POPftlcS cf the' gf'aplntlled TOUnd electrodes are the temperature may be decreased when mixing the coal lleted'lnthe'lcllcwlng Table 4- tar pitch coke and the binding agent, or a binding pitch For he Purpose 0f cOmPaI1S-O11, round electrodes havhaving a higher softening 'peint may be used ing. a diameter of? 7'0 mm. obtained from amoist pitch of Another advantage of the proposed Compounds com the same origin (softening point 57 are fabricated sists in the increase of the yield of coke of the binding Wl'fhout the adflltlon 0f agents Teduclng 'ille softening agent which results in an improvement of the properties peinte cf the blndlngpllches' The softening POlnS 0f of the carbon bodiesl such as an increase of the specific 'ille pitches Used, Whlcll Were llUXed acccdlng 'C0 the weight andthe strength and a lower volume of voids. On invention, were determined in special tests in which the the other hand, in spite of the Vincreased yield of coke, agentfreducing the softening points of the pitches was no change in the physical properties of the coke of the introduced into the pitch with agitation.

TABLE 4 softening Yield of Specino Volume of Flexural Resistance point, coke,1 weight, voids, strength, to pressure, C. percent Y lig/1. percent Jrg/cm.2 lig/cin.2

Dry pitch A 7s 61.1 1.592 22. s 102. 23s Dry pitch .a4-15% of tar 51.5 58, 5 1. 57s 23.1 95 246 Dry pitch b1-20% of heavy tar oil 56 53.v 1. 626 22. 5 100 246 Dry pitch A+10% ofvihyi acetate 50 .54. 2 1. 678 19. 6 114 308 Dry pitch A+5% of siyrehe l 57 59. 9. 1.534. 20.-,9 120 255 Dry pitch ibi-10% of phthalodiui- Y triie 59, 5 73. 0 i. 704 i7. 5 119 347 Dry pitch Pri-10% of acrylonitrile 54, 66. 4 1. 680 19. 4 110 314 Sott pitch without the addition of agents reducing the softeningV point ofthe binding piteh 57 54,8 1. 589 23.0. 97 205 1 Calculated on the pitch and on the agent reducing the softening point` ot the pitch,

binding agent was observed in practice. This phenomenon is of importance especially in the case of carbon bodies that are to be subjected to a subsequent graphitization process. Y i The advantages of the compounds according to the, invention as agents reducing the softening points of the binding pitches as compared with the compounds used hitherto are illustrated by the following examples which,

Example 2 Twenty kilos ofy petrol coke'having the same gradation of grain sizes as in Examplev 1, are mixed at to C. with5 to 5.5 kilos of dry pitch (softening points 79?, 75, 71.5 C.) and the agents reducing the softening points of the binding pitches as listedin the following Tablesl 5V to7, and formed into round electrodesha-ving a diameter of 70 mm., as describedfin Example 1.

. TABLE. 5

softening Yield of Specific Volume of Flcxural Resistance point, coke weight, voids, strength, .to pressure, C. percent kg./1. percent lig-Jem.Z lig/cm.2

Dry pitch A 79. 59.1 1. 548 25. 8 79 196 Dry pitch A|10% of light tar oil.. 60 54. 2v 1. 533 25.8 70 184 Y Dry pitch A+15% of heavy tar oil. 60v 50, 1 1. 507v 27, 1 58 162 Dry pitch A-{-15% of tar 61 54. 0v 1. 542 25. 1 70, 192 Dry pitch A+10% of phthalodiniti-ile 58 70. 3 1. 643 21. 2 92 256 Dry pitch A+l0% of azobciizene 55 62.3, 1. 575 23.3 81 204 Soft pitch (without the addition of agents reducing the softening points) 63. 5 51.6 1. 517 26. O 70 169 TABLE 6 Softening Yield of Specific Volume of Flexural Resistance point, coke, weight, voids, strength, to pressure, C. percent kg./l. percent kgJcm.2 lig/cm.2

Dry pitch B 75 55. 5 1. 565 25. 9 90 205 Dry pitch B+10% of light tar oi1 57 54. 3 1. 544 26. 7 68 173 Dry pitch B|15% of tar 58 56. 1 1. 559 26. 2 69 178 Dry pitch B+10% of phthalodinitrile 47. 5 71. 6 1. 634 22. 4 104 254 Dry pitch B+10% of azobenzene.. 49 62. 0 1. 617 23. 3 98 223 Soft pitch (Without the addition of agents reducing the softening point) 60. 5 53. 5 1. 562 26. 0 79 186 TABLE 7 softening Yield of Specific Volume of Flexural Resistance point, coke, weight, voids, strength, to pressure, C. percent kg./l. percent lig/cin.2 kgJcrn.2

Dry pitch C 71. 5 57.4 1. 572 24. 4 85 213 Dry pitch C-l-10% of light tar oil.. 54. 5 56.0 1. 550 25.0 77 204 Dry pitch (E4-15% of heavy tar oil. 53 55. 9 1. 545 25. 8 69 210 Dry pitch (E4-15% of tar 54 57. 1 1. 574 25. 2 87 230 Dry pitch C+10% of azobenzene 47. 5 60. 7 1. 582 24. 1 95 240 Dry pitch C+10% of phthalodinitrile 48 68. 2 1. 611 24. 1 114 269 Soft pitch (Without the addition of agents reducing the softening point) 60. 5 56. 4 1. 565 25. 6 89 223 Example 3 also a substantial increase inthe yield of coke. Moreover,

Twenty kilos of petrol coke having the same gradation of grain sizes as in Examples 1 and 2 are mixed with ap- 30 the quality of the carbon body is distinctly improved due to the increase in the specific Weight and the strength values as well as on account of the lower volume of voids. The values lie, in `all cases, even distinctly `above the Values of the reference samples obtained with the use of the original dry pitch, although the softening point was decreased considerably.

TABLE 8 Softening Yield of Specific Volume o Flexural Resistance point, coke, weight, voids, strength, to pressure, C. percent kg./l. percent lig/cm.2 kg./cm.2

Ultra dr itch-l-ZO? of light tar @n ff 7i e7. s 1. 59o 23. 7 106 23s Ultra dry pitch-H0 D -I-10% of phthalodinitrile-. 55 80. 5 l. 645 20. 4 115 306 Ultra dry pitch-l-5% of sty e +15% of phthalodinitrile 77 85. 2 1. 650 17. 9 136 354 The examples cited distinctly show the superiority of It has become possible to Work up pitches having a very high softening point by using mixtures of the proposed agents reducing the softening points of the binding pitch, 50 the superiority of these substances as compared with the agents used hitherto again manifesting itself.

TABLE 1 C=C and CEC-4 Addition to the binding softening Yield of pitch, point, C. coke, percent percent Propargyl alcohol CH-C-CHQOH 10 49. 5 (56) 48 (41.5)

Indene 10 27. 5 (57) 46 (42) I 4e (7s) 55 (51) A cenaphthylene 10 43 (62) 50. 5 (43. 5)

Dicyclopentadiene l 10 40 (62) 48 (43. 5)

|C 5o (s1. 5) 54 (5o) TABLE 2-Continued Addition to the binding softening Yield of pitch, point, C. coke, percent percent Cumarinic acid lactone I 10 43 (63. 5) 47 (43.5)

2a1lyloxyanthraquinonc \-O-CH2-CH=CH2 10 56. 5 (63.5) 55.5 (49.5)

Phenyl isocyanate -N=C=O 10 52 (5G) 44. 5 (41. 5)

TABLE 3 C=N- or -CEN1 Addition to the binding Soitening Yield of pitch, point, C. coke, percent percent Cyanoacetic acid NEC-CH2C O OE 10 54 (57) 51 (42) Malonic acid dinitrile NEC-CHz-GEN 53 (57) 5l (42) Benzonitrilc CEN 10 30. 5 (57) 49. 5 (42) Adipic acid nitrilc NEC-CHz-CH2*CH2*CH2CEN 10 81 (63. 5) 49 (44) Phenyl isocyanate N=C=O 10 52 (56) 44. 5 (41. 5)

Succinodinitrile NEG-CHz-CHzEOMN 10 55 (78) 52 (50. 5) Bcnzalaniline C6H5N=CHCH5 10 69 (78) 53. 5 (50. 5)

We claim:

1. A process for the fabrication of carbon bodies which comprises shaping into a body a mixture containing lgrained coke, a binding pitch and an organic compound for reducing the softening point of the binding pitch, said organic compound Ibeing a member selected from the grou-p consisting of vinyl acetate, styrene, phthalodinitrile, acrylonitrile, azobenzene, propargyl alcohol, indene, acenaphthylene, dicyclopentadiene, turpentine oil, divinyl benzene, l,-dimorpholinyl-hexadiyne- 2,4, N-,-chlorallyl-morpholine, methaorylic acid, crotonic acid, vinyl propionate, dibutyl maleate, 1,4-dicyclohexanolyl diacetylene, 2 butylidene-cyclohexanone 1, acetyl acetone, succini'mide, naphthalene dialdehyde, benzil, -anthraquinone, `cumarinic acid lactone, 2-ally-loxyanthraquinone, phenyl isocyanate, cyanoacetic acid, malonic acid dinitrile, benzonitrile, `adipic acid nitrile, succinodinitrile and benzalaniline, said compound being present in an amount of from about 2% to about 20% by Weight calculated on the Weight of the binding pitch; and baking the body at a temperature of about 1000" C.

2. In a method of producing shaped and hardened carbon bodies by admixing granular' coke with a binding pitch, shaping the resulting mixture and baking it, the improvement which comprises adding, prior to the shaping step, from about 2% to about 20% by Weight, calculated on the Weight of binding pitch, of vinyl acetate.

3. In a method of producing shaped and hardened carbon bodies by admixing .granular coke with a binding pitch, shaping the resulting mixture and baking it, the improvement which comprises adding, prior to the shaping step, from about 2% to about 20% by Weight, calculated on the weight of binding pitch, of styrene.

4. In a method of producing shaped and hardened carbon bodies by admixing granular coke with a binding pitch, shaping lthe resulting mixture and baking it, the improvement which comprises adding, prior to the shaping step, from about 2% to about 20% by weight, calculated on the weight of binding pitch, of phthalodinitrile.

5. In a method of producing shaped and hardened carbon bodies by admixing 'granular coke with a binding pitch, shaping the resulting mixture and baking it, the improvement which comprises adding, prior to the shaping step, from about 2% to `about 20% by weight, calculated on the Weight of binding pitch, of aorylonitrilc.

6. In a method of producing shaped and hardened carbon bodies by admixing granular coke with a binding pitch, shaping the resul-ting mixture and baking it, the improvement which comprises adding, prior to the shaping step, from `about 2% to about 20% by Weight, calculated on the Weight of binding pitch, of azobenzene.

Shea etal Oct. 31, 1950 Bushong et al Sept. 4, 1956 

1. A PROCESS FOR THE FABRICATION OF CARBON BODIES WHICH COMPRISES SHAPING INTO A BODY A MIXTURE CONTAINING GRAINED COKE, A BINDING PITCH AND AN ORGANIC COMPOUND FOR REDUCING THE SOFTENING POINT OF THE BINDING PITCH, SAID ORGANIC COMPOUND BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OF VINYL ACETATE, STYRENE, PHTHAIODNITRILE, ACRYLONITRILE, AZOBENZENE, PROPARGYL ALCOHOL, INDENE, ACENAPHTYLENE, DICYCLOPENTADIENE, TURPENTINE OIL, DIVINYL BENZENE, 1,6-DIMORPHOLINYL-HEXADIYNE2,4, N-B-CHLORALLYL-MORPHOLINE, METHACRYLIC ACID, CROTONIC ACID, VINYL PROPIONATE, DIBUTYL MALEATE, 1,4-DICYCLOHEXANOLYL-DIACETYLENE, 2-BUTYLIDENE-CYCLOHEXANONE-1, ACETYL ACETONE, SUCCINIMIDE NAPHTHALENE DIALDEHYDE, BENZIL, ANTHRAQUINONE, CUMARINIC ACID LACTONE, 2-ALLYLOXYANTHRAQUINONE, PHENYL ISOCYANATE, CYANOACETIC ACID, MALONIC ACID DINITRILE, BENZONITRILE, ADIPIC ACID NITRILE, SUCCINODINITRILE AND BENZALANILINE, SAID COMPOUND BEING 